João M. Lemos

Drug Delivery for Neuromuscular Blockade With Supervised Multimodel Adaptive Control

A major issue in drug delivery systems is the high level of uncertainty due to inter- and intrapatient variations in the dynamics of drug absorption and metabolism. This paper proposes an approach to tackle this problem based on supervised multimodel adaptive control (SMMAC). Although the specific case of neuromuscular-blockade-level control of patients subject to general anesthesia is considered, the overall procedure can be applied to the control of other physiological variables. Design guidelines to implement SMMAC are presented, together with clinical cases of patients undergoing general anesthesia, where atracurium is used as the blocking agent. The important role played by the selection of the observer polynomial in the supervisor is demonstrated.

A New Hand-Held Microsystem Architecture for Biological Analysis

This paper presents a hand-held microsystem based on new fully integrated magnetoresistive biochips for biomolecular recognition (DNA hybridization, antibody antigen interaction, etc.). Magnetoresistive chip surfaces are chemically treated, enabling the immobilization of probe biomolecules such as DNA or antibodies. Fluid handling is also integrated in the biochip. The proposed microsystem not only integrates the biochip, which is an array of 16times16 magnetoresistive sensors, but it also provides all the electronic circuitry for addressing and reading out each transducer. The proposed architecture and circuits were specifically designed for achieving a compact, programmable and portable microsystem. The microsystem also integrates a hand-held analyzer connected through a wireless channel. A prototype of the system was already developed and detection of magnetic nanoparticles was obtained. This indicates that the system may be used for magnetic label based bioassays

Local identifiability and sensitivity analysis of neuromuscular blockade and depth of hypnosis models

This paper addresses the local identifiability and sensitivity properties of two classes of Wiener models for the neuromuscular blockade and depth of hypnosis, when drug dose profiles like the ones commonly administered in the clinical practice are used as model inputs. The local parameter identifiability was assessed based on the singular value decomposition of the normalized sensitivity matrix. For the given input signal excitation, the results show an over-parameterization of the standard pharmacokinetic/pharmacodynamic models. The same identifiability assessment was performed on recently proposed minimally parameterized parsimonious models for both the neuromuscular blockade and the depth of hypnosis. The results show that the majority of the model parameters are identifiable from the available input-output data. This indicates that any identification strategy based on the minimally parameterized parsimonious Wiener models for the neuromuscular blockade and for the depth of hypnosis is likely to be more successful than if standard models are used.

Nonlinear Adaptive Control

Exact linear models are obtained using the technique known as input–output feedback linearization, that is applied to a bilinear finite-dimensional state-space approximation of the dynamics of a distributed collector solar field. A control Lyapunov function is then used to jointly design the adaptation law for the uncertain parameter that measures the mirror efficiency, and the gain of the pole-placement controller. Provided that the plant is represented by the finite-dimensional bilinear model considered, this approaches ensures the stability of the overall controlled system, and that the outlet fluid temperature asymptotically approaches the reference. A reduced complexity controller designed along these lines is obtained and the resulting internal state dynamics is studied. Experimental results on a distributed collector solar field are shown.

Distributed Linear-Quadratic Control of Serially Chained Systems: Application to a Water Delivery Canal [Applications of Control]

Networks are prevalent in many human activities such as communication, transport, energy, and water delivery and drainage. Large networks that spread over wide-space areas cross the borders of different administrative regions, or even countries, and are managed by regional decision centers that may have to comply with different legal requirements. With networking comes complexity and the need to coordinate local decisions, which is an issue for which control and optimization can provide significant contributions. The sources of complexity are many, including the heterogeneous nature of some information patterns and the need to perform control over communication networks that may fail or have varying delays. This article does not attempt to address all of these issues. Instead, the attention is concentrated on how to design distributed controllers for plants that can be modeled by the serial interconnection of subsystems.

A 2 -VM: a cooperative Java VM with support for resource-awareness and cluster-wide thread scheduling

In todays scenarios of large scale computing and service providing, the deployment of distributed infrastructures, namely computer clusters, is a very active research area. In recent years, the use ofGrids, Utility and Cloud Computing, shows that these are approaches with growing interest and applicability, as well as scientific and also commercial impact. n nThis work presents the design and implementation issues of a cooperative VM for a distributed execution environment that is resource-aware and policy-driven. Nodes cooperate to achieve efficient management of the available local and global resources. We propose A2-VM, a cooperative cluster-enabled virtual execution environment for Java, to be deployed on Grid sites and Cloud data-centers that usually comprise a number of federated clusters. This cooperative VM has the ability to monitor base mechanisms (e.g. thread scheduling, garbage collection, memory or network consumptions) to assess applications performance and reconfigure these mechanisms in run-time according to previously defined resource allocation policies. n nWe have designed this new cluster runtime by extending the Jikes Research Virtual Machine to incorporate resource awareness (namely resource consumption and restrictions), and extending the TerraCotta DSO with a distributed thread scheduling mechanism driven by policies that take into account resource utilization. In this paper we also discuss the cost of activating such mechanisms, focusing on the overhead of measuring/metering resource usage and performing policy evaluation.

Temperature Control of a Solar Furnace with Exact Linearization and Off-Line Identification

The ability to predict the behavior of materials is crucial in several industries due to safety aspects, such as in high temperature furnaces for the production of glass, in the nuclear energy industry or in the high concentrated thermal solar systems. Solar furnaces use concentrated solar radiation that can be used to perform material stress tests with high temperatures. These devices have nonlinear dynamics that are caused by the actuator, the shutter, and by the interaction between the solar energy and the properties of the material. The contribution of this paper consists in the design of a controller for practical use based on the exact linearization method with off-line identification. The aim is to improve the controller performance to track the temperature profile. In this context it is assumed that the thermodynamic properties of the sample material to be tested are unknown.

Control of a solar furnace using active cooling

This paper explores a control architecture for a solar furnace that uses active cooling to improve the temperature reference tracking during the decreasing phase of the reference. This is done in conjunction with the command of the shutter that adjusts the incident power and compensates sun power variability due to weather conditions. The controller uses exact linerization coupled with a PI controller to handle model parameter uncertainty. Off-line identification is employed to characterize the temperature dynamics, this is used to avoid online adaptation mechanisms that may cause stability problems during the controller startup, that may melt the material sample. Experimental results obtained from the plant in closed loop control using active cooling are presented.

Temperature control of a solar tower receiver based on the Lyapunov method

This article describes an approach to design a temperature controller for a solar tower receiver that receives concentrated solar energy from a field of heliostats and is employed to transfers energy to a heat transfer fluid (HTF), such as molten salt. During the operation of solar receiver, its temperature and the temperature of the HTF fluid must be controlled to obtain the maximum economical yield constrained by operational safety margins and by the designed life span of the receiver. To attain this purpose, fluid flow and the positions of the heliostats are used as manipulated variables to control the error between the temperature reference and the temperature of the fluid at the receiver outlet. The presence of disturbances is an important factor to consider during the receiver operation. They include solar energy fluctuations caused by weather conditions, presence of moving clouds, the apparent movement of the sun, and wind that can change energy losses. The controller is designed in two steps. In the first step, the thermal stationary operating point of the solar receiver is defined and is used to build a nonlinear dynamical equation of the temperature error. In the second step, the stability of the nonlinear error dynamics, that depends on the speed of the fluid and on the concentrating power of the heliostats, is analyzed using the Lyapunov method. From this analysis the control system is defined, resulting in a nonlinear feed-forward term used to compensate the solar energy fluctuations, and a statefeedback controller that adjusts the the fluid flow to compensate temperature deviations from the temperature reference.

Material derivative based control of a solar parabolic trough field

This paper considers the temperature control of a concentrating solar power (CSP) parabolic trough system, where sun energy is harvested to produce thermal and electrical energy. In this process, the temperature of the heat transfer fluid depends on the solar power variability and on the solar exposure time and is described by a partial differential equation (PDE). To control the temperature, the speed of the fluid is used as the the manipulated variable. The dynamics of this process is usually represented using a time-varying state space model. The solution of the PDE is interpreted from the material derivative description point of view and is used to formulate an optimal constrained control problem of the state of an infinitesimal volume element, defined by its temperature and its position, with free final time and fix terminal state. The control problem is then extended to the whole fluid inside the pipe, where the state of the fluid is represented by the set of states of infinitesimal volume elements without the need to use a time-varying state space model of the process. From this work, a control law with simple structure is obtained that fulfills the performance objectives.